acarus /ˈæk.ə.ɹəs/ noun1 •Any member of the subclass Acari (aka Acarina): thus, a mite or a tick; specifically, any mite of the genus Acarus.The number of Acari found in raw sugar is sometimes exceedingly great, and in no instance is the article quite free from either the insects or their ova (eggs). — 1868 formsacari · acarina